Clients still ask me if the colored squares on toothpaste boxes “code” the formula — nope; they’re just eyemarks for the fin-seal/cutter sensors, with the color picked purely for contrast against the print. On a tube line I art-directed in May 2024 we spec’d a 5 mm black eyemark near the crimp; do you call it an eyemark or a registration mark where you work?
Eyemark here too, not ‘registration mark’ — that’s plate alignment; think of it as the cutter’s barcode cousin, and ask the line which sensor (RGB vs IR) they use so you can spec high contrast in that band, e.g., white on dark or rich black on light. On glossy/metallized film we get better reads with a tiny matte patch or rich black (C60 M40 Y40 K100) instead of pure K. Curious if you ever tuck it into a color bar to keep brand folks calm.
I’ve had misreads when the mark sat under matte OPV, so I spec “no OPV over eyemark” and a 2 mm clear zone, even on a “5 mm black near the crimp.” If the background’s metallic, I add a white underlay with 100K on top; otherwise straight 100K works — does your line allow varnish windows?
Spec 5 mm K by the crimp, but ‘no trap’ prevents RGB misreads.